Hi In my opinion you should try to get in touch with willem first. He also maintains a mp PKGBUILD (As a split PKGBUILD). As I understand from a first glance, both are using the same source and as unnecessary duplicates should be avoided, one PKGBUILD could be merged into the other. And then the issue with ncurses could be solved.
Best regards Regarding ________  https://aur.archlinux.org/pkgbase/mp-5/